FRACTURE PARAMETERS EVALUATION FOR THE CRACKED NONHOMOGENEOUS ENAMEL BASED ON THE FINITE ELEMENT METHOD AND VIRTUAL CRACK CLOSURE TECHNIQUE

To accurately solve the fracture parameters of enamel, we have established computational nonhomogeneous enamel models and constructed the fracture element of enamel dumb nodes, based on the enamel mineral concentration, nonhomogeneous mechanical properties, and virtual crack closure technique. Through the commercial finite element software ABAQUS and the fracture element of the enamel dumb nodes, we have established the user subroutines UMAT and UEL, which enabled solving of the energy release rates of the nonhomogeneous enamel structure with cracks. The stress intensity factors of central cracks, three-point bend and compact stretched enamels, and double-edge notched stretched enamels are determined. By comparing them with analytical solutions, we have proved that the fracture element of the enamel dumb nodes is highly accurate, simple, and convenient. In addition, the cracks can be other elements rather than singular or special elements; they show versatility and other advantages. The stress intensity factor of the dental enamel can be solved more realistically. Thus, a new numerical method for prevention and treatment of dental diseases is provided

Mid-infrared variability of changing-look AGN

It is known that some active galactic nuclei (AGNs) transited from type 1 to type 2 or vice versa. There are two explanations for the so-called changing look AGNs: one is the dramatic change of the obscuration along the line-of-sight, the other is the variation of accretion rate. In this paper, we report the detection of large amplitude variations in the mid-infrared luminosity during the transitions in 10 changing look AGNs using WISE and newly released NEOWISE-R data. The mid-infrared light curves of 10 objects echoes the variability in the optical band with a time lag expected for dust reprocessing. The large variability amplitude is inconsistent with the scenario of varying obscuration, rather supports the scheme of dramatic change in the accretion rate.Comment: Published by ApjL, 7 pages, 3 figures, 2 table

Fine root morphology and growth in response to nitrogen addition through drip fertigation in a Populus × euramericana “Guariento” plantation over multiple years

International audienceAbstractKey messageNitrogen addition through drip fertigation to a poplar plantation (Populus × euramericana“Guariento”) promoted fine root growth only in the early period. The relationship between root growth and soil N content was positive in the first 2 years, but became negative in the third year when the soil N availability had substantially increased.ContextNitrogen (N) deficiency is common in forest soils, and N addition is sometimes applied in the case of intensive plantations. There is a need to better document the impact of N addition through the high-efficiency fertilization technique on fine root morphology and growth, given their importance for the uptake of nutrients and for tree growth.AimsWe aimed to quantitatively investigate the responses of fine roots in morphology and growth to N addition through surface drip fertigation over multiple years in a Populus × euramericana “Guariento” plantation.MethodsA field experiment that included four drip fertigation treatments with N addition levels (0, 60, 120, and 180 kg N ha−1 year−1) was conducted for three successive years. A coring method was used to sample soils and quantify the root morphological traits and soil N content along 0–60-cm profiles.ResultsThe root biomass density, length, surface area, specific length, and tissue density were significantly higher in the N addition treatments than those in the control after the first year, but the positive effect decreased in the second year. In the third year, root biomass in the N addition treatments was even lower by 11–39% than that in the control. The relationship between root growth and soil N content was also positive in the first 2 years and negative in the third year.ConclusionN addition promoted fine root growth mainly in the shallow soil and in the early period of experiment. The relationship between root growth and soil N content became negative in the third year when the soil N availability had substantially increased. It is suggested that fine roots adjust their growth and morphology in response to N availability varying along the soil profile and with the fertilization duration

Discovery of a Mid-infrared Echo from the TDE candidate in the nucleus of ULIRG F01004-2237

We present the mid-infrared (MIR) light curves (LCs) of a tidal disruption event (TDE) candidate in the center of a nearby ultraluminous infrared galaxy (ULIRG) F01004-2237 using archival {\it WISE} and {\it NEOWISE} data from 2010 to 2016. At the peak of the optical flare, F01004-2237 was IR quiescent. About three years later, its MIR fluxes have shown a steady increase, rising by 1.34 and 1.04 mag in $3.4$ and $4.6\mu$m up to the end of 2016. The host-subtracted MIR peak luminosity is $2-3\times10^{44}$\,erg\,s$^{-1}$. We interpret the MIR LCs as an infrared echo, i.e. dust reprocessed emission of the optical flare. Fitting the MIR LCs using our dust model, we infer a dust torus of the size of a few parsecs at some inclined angle. The derived dust temperatures range from $590-850$\,K, and the warm dust mass is $\sim7\,M_{\odot}$. Such a large mass implies that the dust cannot be newly formed. We also derive the UV luminosity of $4-11\times10^{44}$\,erg\,s$^{-1}$. The inferred total IR energy is $1-2\times10^{52}$\,erg, suggesting a large dust covering factor. Finally, our dust model suggests that the long tail of the optical flare could be due to dust scattering

Mid-infrared flare of TDE candidate PS16dtm: dust echo and implications for the spectral evolution

PS16dtm was classified as a candidate tidal disruption event (TDE) in a dwarf Seyfert 1 galaxy with low-mass black hole ($\sim10^6M\odot$) and has presented various intriguing photometric and spectra characteristics. Using the archival WISE and the newly released NEOWISE data, we found PS16dtm is experiencing a mid-infrared (MIR) flare which started $\sim11$ days before the first optical detection. Interpreting the MIR flare as a dust echo requires close pre-existing dust with a high covering factor, and suggests the optical flare may have brightened slowly for some time before it became bright detectable from the ground. More evidence is given at the later epochs. At the peak of the optical light curve, the new inner radius of the dust torus has grown to much larger size, a factor of 7 of the initial radius due to strong radiation field. At $\sim150$ days after the first optical detection, the dust temperature has dropped well below the sublimation temperature. Other peculiar spectral features shown by PS16dtm are the transient, prominent FeII emission lines and outflows indicated by broad absorption lines detected during the optical flare. Our model explains the enhanced FeII emission from iron newly released from the evaporated dust. The observed broad absorption line outflow could be explained by accelerated gas in the dust torus due to the radiation pressure.Comment: Accepted by ApJ, 5 figure

Cullin4 E3 ubiquitin ligases regulate male gonocyte migration, proliferation and blood-testis barrier homeostasis

Ubiquitination, an essential posttranslational modification, plays fundamental roles during mammalian spermatogenesis. We previously reported the requirement of two Cullin 4 ubiquitin ligase family genes, Cullin 4a

Characterization of grass carp reovirus minor core protein VP4

<p>Abstract</p> <p>Background</p> <p>Grass Carp Reovirus (GCRV), a tentative member in the genus <it>Aquareovirus</it> of family <it>Reoviridae</it>, contains eleven segmented (double-stranded RNA<b>)</b> dsRNA genome which encodes 12 proteins. A low-copy core component protein VP4, encoded by the viral genome segment 5(S5), has been suggested to play a key role in viral genome transcription and replication.</p> <p>Results</p> <p>To understand the role of minor core protein VP4 played in molecular pathogenesis during GCRV infection, the recombinant GCRV VP4 gene was constructed and expressed in both prokaryotic and mammalian cells in this investigation. The recombinant His-tag fusion VP4 products expressed in E.<it>coli</it> were identified by Western blotting utilizing His-tag specific monoclonal and GCRV polyclonal antibodies. In addition, the expression of VP4 in GCRV infected cells, appeared in granules structure concentrated mainly in the cytoplasm, can be detected by Immunofluorescence (IF) using prepared anti-VP4 polyclonal antibody. Meanwhile, VP4 protein in GCRV core and infected cell lysate was identified by Immunoblotting (IB) assay. Of particular note, the VP4 protein was exhibited a diffuse distribution in the cytoplasm and nucleus in transfected cells, suggesting that VP4 protein may play a partial role in the nucleus by regulating cell cycle besides its predicted cytoplasmic function in GCRV infection.</p> <p>Conclusions</p> <p>Our results indicate the VP4 is a core component in GCRV. The cellular localization of VP4 is correlated with its predicted function. The data provide a foundation for further studies aimed at understanding the role of VP4 in viroplasmic inclusion bodies (VIB) formation during GCRV replication and assembly.</p